Smart van der Waals Sieves

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Our society heavily relies on various porous materials, which are used for filtration, gas separation, desalination, etc. As pore sizes become smaller and better defined, increasingly enhanced selectivity and performance characteristics can be achieved. While functional porous materials such as zeolites and metal-organic frameworks offer intrinsic molecule-size pores, they are hard to be integrated for nanoscale detection and characterization capabilities. Meanwhile, modern microfabrication techniques used to make integrated semiconducting circuits, have so far been unable to reliably create pores with size down to that of individual molecules.Here I propose a radically new top-down approach that allows nanofabrication of pores at the true atomic scale by assembling van der Waals (vdW) crystals in designer sequences. This involves disassembly of layered bulk crystals into individual atomically thin layers, followed by reassembly of these layers into artificial heterostructures. The proposed smart vdW sieving devices would combine molecular separation functions of well-defined nanopores with detection functions of modern chromatography. The whole device can be reduced in size to that of a tiny microchip.To realize such multifunctional compact wonder sieves, extensive work is first required to obtain electrical and optical characteristics of various molecules of interest confined inside atomic-scale slits, because structural and transport characteristics under strong confinement are expected to differ drastically from those in the bulk. In parallel, we will develop efficient molecular sieving through these vdW slits using a combination of steric and electrostatic exclusion. With such fundamental understanding of structural characteristics and transport mechanisms at the molecular scale, my team and I will demonstrate smart integrated sieves (lab-on-a-chip technology at atomic-scale) for simultaneous separation and detection of various molecules.